Development of viscoelastic tubes similar to blood pump

本研究的目的是制造粘弹性管，这是解剖学上相同，功能等同于天然主动脉。一个旋转成型工作站，最初是在新加坡国立大学开发的用于这项研究。首先，我们尝试以传统的方法制作主动脉弓状管，在模具上以刷子涂上硅油后，使用单一的旋转轴。然而，很难制造均匀厚度的管，并且也很难控制质量。接下来，使用旋转成型工作站在两个轴之间的旋转速度的各种组合下以不同的喷涂体积、间隔和时间进行了多次试验和错误。最后确定了1 mm厚管的最佳成型条件为：长、短轴转速分别为0.02rpm和8 rpm，硅胶用量为20 g，喷涂3次，喷涂间隔时间为3 h。天然主动脉具有特殊的力学特性，在容积增量较小的范围内，压力增加较小，而在容积增量较大的范围内，压力增加较大。我们曾尝试过多层管的制作，但没有得到满意的结果。因此，进行了包含与硅胶不同性质的其他试验。海绵层夹有柔软和坚硬的硅树脂层。该三层管的柔度在小体积增量40%时为0.411/mmHg，但在40%以上时下降到0.361/mmHg，这是由于主要弹性效应由外层硬硅向内层软硅转移的结果，这一发现对滚塑机的进一步改进具有参考价值。

The purpose of this study was to fabricate viscoelastic tubes, which was anatomically identical and functionally equivalent to the natural aorta. A rotational molding workstation which was originally developed at the National University of Singapore was used for this research. First of all, we tried to fabricate aortic arch-shaped tubes by a conventional method ; a single rotational axis was employed after silicone liquid was painted onto the mold by a brush. However, it was hard to make an even thickness tube, and it was also hard to control the quality. For the next step, several trials and errors were conducted using a rotational molding workstation under various combination of rotational speeds between two axis with different painting volume, interval and times. At last, the optimal condition to develop 1mm-thickness tube was determined as follows : rotational speeds of major and minor axis were 0.02rpm and 8rpm, respectively, a weight of silicone was 20g each for three times, and painting interval was 3hours. Then, thickness deviation which was defined as a ratio between standard deviation and average thickness culd be reduced from 30% to 20%.It was well-known that natural aorta had specific mechanical properties ; increase in pressure is small for the range of less incremental volume, whereas it becomes more for the range of higher incremental volume. We have tried to fabricated multi-layr tube, however, we haven't get a favorable result. So, other trials that contained different properties from silicone was carried out. A sponge layr was sandwiched with soft and stiff silicone layrs. The compliance values of this 3-layr tube was 0.41 1/mmHg in the range of small incremental volume up tp 40%, but it was decreased to 0.36 1/mmHg for over 40%, due to a shift of major elasctic effects from outer stiff to inner soft silicon layr.Above findings were worthwhile for the further improvements of the rotational molding machine.